1. Field of the Invention
The present invention relates to a document processing system and, more particularly, to a document processing system with printing pitch change and display functions.
2. Description of the Prior Art
In conventional typewriters or the like, so-called proportional printing can be performed wherein the pitch of characters to be printed can be arbitrarily changed. Predetermined pitches are assigned to the character type to be used. A carriage drive controls positions of characters to be printed in accordance with the predetermined pitch. Three pitches, i.e., 10 pitch (pica), 12 pitch (elite) and 15 pitch (micron) are adapted as references for proportional printing elements. Type widths and shapes of printing elements (e.g., printing wheels) are determined in accordance with the pitch references. A user must set the reference pitch at a keyboard or switch means so as to obtain printing that matches the mounted printing wheel. An electronic typewriter with an automatic printing pitch setting function has been recently developed. According to this typewriter, a reference pitch of a printing wheel set in the typewriter is automatically detected optically or by the shape of the wheel, and the corresponding printing pitch can be automatically set.
It is important for an operator to properly know which printing pitch is currently set in the document processing apparatus. However, printing pitch information varies. For example, normal manual printing pitches consist of pica (10 characters/inch, fixed), elite (12 characters/inch, fixed), micron (15 characters/inch, fixed), pica-based proportional 1, elite-based proportional 2, and micron-based proportional 3. When information representing whether or not the pitch is manually selected or automatically selected in accordance with the pitch of the printing wheel loaded in the document processing apparatus is included in the display information, the amount of displayed information is increased. Therefore, the number of components for pitch selection and display operations is increased, thus requiring a large space. Furthermore, in a conventional document processing apparatus, the user must open the cover and insert a printing element upon energization of the apparatus.